Soundproof enclosure



FIG. 1 is a perspective view of a soundproof enclosure, showing my new design;

FIG. 2 is a left side elevation view, the right side elevation view being a mirror image thereof;

FIG. 3 is a rear elevation view;

FIG. 4 is a front elevation view;

FIG. 5 is a top plan view; and,

FIG. 6 is a bottom plan view. 

The ornamental design for a soundproof enclosure, as shown and described. 